var _PADCHAR = "=",
      _ALPHA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
      _VERSION = "1.1";//Mr. Ruan fix to 1.1 to support asian char(utf8)
     
     
    function _getbyte64( s, i ) {
      // This is oddly fast, except on Chrome/V8.
      // Minimal or no improvement in performance by using a
      // object with properties mapping chars to value (eg. 'A': 0)
     
      var idx = _ALPHA.indexOf( s.charAt( i ) );
     
      if ( idx === -1 ) {
        throw "Cannot decode base64";
      }
     
      return idx;
    }
     
    function _decode_chars(y, x){
        while(y.length > 0){
          var ch = y[0];
          if(ch < 0x80) {
              y.shift();
              x.push(String.fromCharCode(ch));
          }else if((ch & 0x80) == 0xc0){
              if(y.length < 2) break;
              ch = y.shift();
              var ch1 = y.shift();
              x.push(String.fromCharCode( ((ch & 0x1f) << 6) + (ch1 & 0x3f)));
          }else{
              if(y.length < 3) break;
              ch = y.shift();
              var ch1 = y.shift();
              var ch2 = y.shift();
              x.push(String.fromCharCode(((ch & 0x0f) << 12) + ((ch1 & 0x3f) << 6) + (ch2 & 0x3f)));
          }    
        }
    }
     
    function _decode( s ) {
      var pads = 0,
        i,
        b10,
        imax = s.length,
        x = [],
        y = [];
     
      s = String( s );
       
      if ( imax === 0 ) {
        return s;
      }
     
      if ( imax % 4 !== 0 ) {
        throw "Cannot decode base64";
      }
     
      if ( s.charAt( imax - 1 ) === _PADCHAR ) {
        pads = 1;
     
        if ( s.charAt( imax - 2 ) === _PADCHAR ) {
          pads = 2;
        }
     
        // either way, we want to ignore this last block
        imax -= 4;
      }
     
      for ( i = 0; i < imax; i += 4 ) {
        var ch1 = _getbyte64( s, i );
        var ch2 = _getbyte64( s, i + 1);
        var ch3 = _getbyte64( s, i + 2);
        var ch4 = _getbyte64( s, i + 3);
         
        b10 = ( _getbyte64( s, i ) << 18 ) | ( _getbyte64( s, i + 1 ) << 12 ) | ( _getbyte64( s, i + 2 ) << 6 ) | _getbyte64( s, i + 3 );
        y.push(b10 >> 16);
        y.push((b10 >> 8) & 0xff);
        y.push(b10 & 0xff);
        _decode_chars(y, x);
      }
      switch ( pads ) {
        case 1:
          b10 = ( _getbyte64( s, i ) << 18 ) | ( _getbyte64( s, i + 1 ) << 12 ) | ( _getbyte64( s, i + 2 ) << 6 );
          y.push(b10 >> 16);
          y.push((b10 >> 8) & 0xff);
          break;
     
        case 2:
          b10 = ( _getbyte64( s, i ) << 18) | ( _getbyte64( s, i + 1 ) << 12 );
          y.push(b10 >> 16);
          break;
      }
      _decode_chars(y, x);
      if(y.length > 0) throw "Cannot decode base64";
      return x.join( "" );
    }
     
     
    function _get_chars(ch, y){
      if(ch < 0x80) y.push(ch);
      else if(ch < 0x800){
          y.push(0xc0 + ((ch >> 6) & 0x1f));
          y.push(0x80 + (ch & 0x3f));
      }else{
          y.push(0xe0 + ((ch >> 12) & 0xf));
          y.push(0x80 + ((ch >> 6) & 0x3f));
          y.push(0x80 + (ch & 0x3f));
      }
    }
     
     
    export const encode =  function( s ) {
      if ( arguments.length !== 1 ) {
        throw "SyntaxError: exactly one argument required";
      }
     
      s = String( s );
      if ( s.length === 0 ) {
        return s;
      }
       
      var i,
        b10,
        y = [],
        x = [],
        len = s.length;
      i = 0;
      while(i < len){
          _get_chars(s.charCodeAt(i), y);
          while(y.length >= 3){
              var ch1 = y.shift();
              var ch2 = y.shift();
              var ch3 = y.shift();
              b10 = ( ch1 << 16 ) | ( ch2 << 8 ) | ch3;
              x.push( _ALPHA.charAt( b10 >> 18 ) );
              x.push( _ALPHA.charAt( ( b10 >> 12 ) & 0x3F ) );
              x.push( _ALPHA.charAt( ( b10 >> 6 ) & 0x3f ) );
              x.push( _ALPHA.charAt( b10 & 0x3f ) );
          }
          i++;
      }
        
     
      switch ( y.length ) {
        case 1:
          var ch = y.shift();
          b10 = ch << 16;
          x.push( _ALPHA.charAt( b10 >> 18 ) + _ALPHA.charAt( ( b10 >> 12 ) & 0x3F ) + _PADCHAR + _PADCHAR );
          break;
     
        case 2:
          var ch1 = y.shift();
          var ch2 = y.shift();
          b10 = ( ch1 << 16 ) | ( ch2 << 8 );
          x.push( _ALPHA.charAt( b10 >> 18 ) + _ALPHA.charAt( ( b10 >> 12 ) & 0x3F ) + _ALPHA.charAt( ( b10 >> 6 ) & 0x3f ) + _PADCHAR );
          break;
      }
     
      return x.join( "" );
    }